The present invention relates to a process for connecting a number of shorts strips of a roll of photographic material.
In today's highly automated photo laboratory, prints are produced from the appropriate kind of materials from which reproductions can be made, e.g., from film negatives, usually by using so-called printers. In order to achieve the highest possible level of efficiency with these printers, first a long roll composed of individual film negative strips is produced with the acid of binding materials and this long roll is then processed by the printer. This technique of connecting individual film negative strips is generally known by the term "splicing".
Especially for the recording of films that have already been developed at an earlier time and have been returned to the customer, the negatives are available only in the form of short strips because they were cut into short strips once the film was developed so that they could be inserted into the return envelope for each individual customer. Normally, the films are cut into four, sometimes into six fields of negatives. Looking at uncut strips from their ends, these yet uncut films have a relatively wide area at the beginning and end of the film in which no picture field exist (film leader or trail) so that a splice can be performed at these points easily and comfortably. In case of the short cut film strips associated with reorders, splicing is not easy because the areas between the first picture field and the last picture field, that is at the back end of the front and the front end of the last film strip of the uncut film strips, are very narrow and are often only 1-2 mm or even smaller. On the other hand, the splice must be clearly identified by a corresponding splice detector because once the paper prints have been produced the long roll must be reduced into the original individual short film strips in order to be able to reinsert the individual film strips into the return envelopes for the customer.
Using a known procedure, the individual film strips are connected in such a way that the film strips are connected along the edges with the aid of a piece of adhesive tape, with a continuous roller positioned parallel to it, for example with a paper strip, to form a long roll of film strips on a roller. For example, on the paper strips, individual fields can be positioned in the picture fields of the film strips to indicate how many paper prints are supposed to be produced from the given negative. This roll of film strips on a roller is then processed by the printer.
Further, a procedure for splicing films is proposed in U.S. Pat. No. 4,468,268 for application in movie theaters. The edges of the film ends to be spliced are cut perpendicular to the longitudinal edges. Then a thin layer of the film material is scratched off, for example with a razor blade, at the narrow edge film sections being spliced. Glue is applied on these scratched surfaces. The edges of the film sections are then placed against each other. Then a connecting piece that covers the scratched off area having been coated with glue is applied or pressed on so that the connecting piece (splice) quasi connects both ends of the film sections to each other.
In principle, both procedures are suitable for connecting such short film strips of the kind found in reorders, but they have disadvantages. The disadvantage of the first splicing procedure described above with its additional roller is that a relatively large additional roller is required, resulting in greater complexity. Another disadvantages is that the resulting roll of film strips on a roller is much wider and harder to handle than a narrow roll of film in comparison with it. Particularly the distances to be covered, the guides, and the work stations must be designed for a correspondingly wide roll of film strips on a roller, placing corresponding space demands on the individual stations in the printer and in any subsequent equipment connected to the printer. Furthermore, one has to take in consideration that the roller and the film strips are continuously connected to each other in parallel fashion and the longitudinal film strips are aligned in sequence so that the width of the roll of film strips on a roller essentially remains the same and does not fluctuate in wide areas. Otherwise the transport distances, guides, and work stations would also have to be designed to accommodate such fluctuations in width. This is especially important in view of the fact that a precise positioning of the film material is necessary in the exposure station so that accurate reproduction of the given picture field of the negative onto the copier print can be assured.
In the case of the other procedure described, the disadvantage is that the surfaces have to be scratched off in a complicated fashion so that glue can be applied. Then the glue has to be applied in another step. Only then can the scratched areas that have been coated with glue be connected to each other by means of the connecting piece (splice) that has to be attached to both surfaces. But a precondition for such splicing is that there is a sufficiently wide area available at the film ends being spliced between the front edge and the first picture field or between the back edge and the last picture field. This surface must be cut in a defined way (perpendicular to the edge of the film) whereby a sufficiently large area has to be left over for the scratching step, the application of glue, and for applying the splice. When films are reordered (their front and back edges have already been cut in a defined fashion), usually only a 1-2 mm area up to the edge is left over at the ends of the individual film strips; often this area is even narrower, which makes the application of splices using the afore-described procedure more difficult. Even if one assumes that the application of a splice is thoroughly reliable, such splicing of films or film strips continues to have considerable disadvantages.
Depending upon the type of glue used, it is either very difficult or not at all possible to remove the splice after processing, which is important in the case of reorders because the film has to be recut into individual strips following reproduction of the prints in order to be able to reinsert these strips into the envelopes belonging to the given customer.
Another disadvantage results from the fact that in the course of the increasingly downscaled size of modern printers due to growing lack of space in photo laboratories, the interior of a modern printer has to be used in better ways. For this purpose, the spliced rolls being processed are fed and redirected along numerous spools in the interior of the printer. Often the rolls are fed across spools having small diameters, such as spools with a diameter of 15 mm or less, and conveyed around 180.degree. turns (e.g., guiding the roll upwards and downwards). If the splice is secured to both ends of the film across the entire width of the film in the fashion described above, then significant difficulties can appear during the transport of the roll, especially in the case of spools having a small diameter and in the case of sharp changes in direction (redirection). For example, the film can bend if the splice is subject to too much pressure, or the narrow splice can break or rip where the glue has been applied. Interruption-free and unencumbered feeding of the roll cannot always be guaranteed using this kind of splicing, especially not if the roll is guided through spools having small diameters and is subject to sharp changes in direction (redirection) as is the case in modern printers, even if one disregards the complicated nature of achieving such splicing to begin with.
Another disadvantage of film strips spliced together in this fashion also results from the fact that the film strips connected together to form a roll on the basis of known methods can bend. This is disadvantageous in view of the fact that in modern printers and other film processing equipment so-called "levelling loops" are often formed that serve to bridge the fluctuations in the speeds of the individual work stations. Should a bend in the roll appear during the formation of such levelling loops, then individual film strips could get caught on each other as a result of such bends and could make it necessary to interrupt printer operations.